Nearpod is a free educational app that you would be crazy not add to your teaching toolkit. Nearpod works in much the same way as the Socrative App in that it turns the iPad into a sophisticated student response system. However, Nearpod has far more capability to integrate media. Nearpod allows you to upload presentations, pdf files, and video to create slides. It also offers interactive elements you can add to the presentation in between slides including: multiple choice questions, polls, short answer questions, drawings, etc...While Socrative works well on the fly, Nearpod requires careful preparation. The results are worth it on the back end. It will e-mail you reports of results on both an individual and whole class basis. Additionally, you can select share and send individual results straight to the students after they post. It has a feature to inform you if a student exited the presentation and allows you to control how the content flows.
Below, I have included two excellent video tutorials brought to my attention via John Evans. The screencasts were made by iPadagody which is based in Australia so they are fun to listen to as well as informative. They each run about 10 minutes and are well worth the time.